A new report on lobbyists shows there are fewer registered now than at any point during the last decade, a falloff that coincides with passage of new federal lobbying restrictions in 2007.

The 2007 rules amended the Lobbying Disclosure Act of 1995 to strengthen the reporting requirements on lobbying, donations and gifts to Congress. In response, some advocates began to reexamine whether their job description was technically lobbying, and many moved to terminate their registration.

The latest figures from the Center for Responsive Politics show that 3,627 lobbyists terminated their registrations in 2008, 1,467 in 2009 and 447 so far this year -- leaving 11,116 to patrol the halls of power as of April 25. The number of registered lobbyists has fallen by nearly 25 percent since 2007.

"I think a lot of people who deregistered probably never should have registered in the first place but did so due to an overabundance of caution, and now they're realizing there is a downside," said Kenneth A. Gross, the head of Skadden, Arps, Slate, Meagher & Flom's political law practice.

The Center for Responsive Politics once attributed the drop to the Obama administration's crackdown on lobbying. But the group now says that is only part of the explanation.

"We found that although Obama's policies may have elevated deregistration numbers, the passage and implementation of [the new lobbying reform] itself had a much larger impact on the number of lobbyists deregistering," the center said in its report released June 30.

Advocates become lobbyists when at least 20 percent of the work they do on behalf of a given client constitutes lobbying. At that point, a contract between the two parties is reported on a special form filed with the clerk of the House of Representatives and the secretary of the Senate. But experts say determining whether that reporting threshold has been surpassed can hinge on something as mundane as whether the drive to meet a public official is recorded or merely the 30 minutes spent on Capitol Hill in a meeting.

"Do I think these people went back to Arkansas and became farmers? No, they just weren't doing it 20 percent anymore," said David Wenhold, president of the American League of Lobbyists. "I think the 20 percent rule needs to be clearly defined and also what the role of a lobbyist is."

Though Wenhold said he does know of large lobbying shops that are closely tracking thresholds and filing fewer registrations, it isn't as though the work for the big players has gone away. A more likely outcome is that the increased reporting requirements and Obama's decision to bar lobbyists from trade advisory boards will push smaller nonprofits and associations, which sometimes have a single individual overseeing government affairs, to send fewer representatives to Capitol Hill, which will tip the scale in favor of interests that can afford a multi-pronged effort of lobbying and advocacy.

"You're really hurting Main Street, whereas Wall Street can afford to send a dozen lobbyists and still have other representatives on the boards," Wenhold said.

Whether Wenhold's prediction is reflected among the lobbyists who have already deregistered will be the subject of an upcoming Center for Responsive Politics report.